nfsd: Use vfs_fsync_range() in nfsd_commit

The NFS COMMIT operation allows the client to specify the exact byte range
that it wishes to sync to disk in order to optimise server performance.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 79d216f..ed024d3 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1141,8 +1141,9 @@ out:
 #ifdef CONFIG_NFSD_V3
 /*
  * Commit all pending writes to stable storage.
- * Strictly speaking, we could sync just the indicated file region here,
- * but there's currently no way we can ask the VFS to do so.
+ *
+ * Note: we only guarantee that data that lies within the range specified
+ * by the 'offset' and 'count' parameters will be synced.
  *
  * Unfortunately we cannot lock the file to make sure we return full WCC
  * data to the client, as locking happens lower down in the filesystem.
@@ -1152,23 +1153,32 @@ nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp,
                loff_t offset, unsigned long count)
 {
        struct file     *file;
-       __be32          err;
+       loff_t          end = LLONG_MAX;
+       __be32          err = nfserr_inval;
 
-       if ((u64)count > ~(u64)offset)
-               return nfserr_inval;
+       if (offset < 0)
+               goto out;
+       if (count != 0) {
+               end = offset + (loff_t)count - 1;
+               if (end < offset)
+                       goto out;
+       }
 
        err = nfsd_open(rqstp, fhp, S_IFREG, NFSD_MAY_WRITE, &file);
        if (err)
-               return err;
+               goto out;
        if (EX_ISSYNC(fhp->fh_export)) {
-               if (file->f_op && file->f_op->fsync) {
-                       err = nfserrno(vfs_fsync(file, file->f_path.dentry, 0));
-               } else {
+               int err2 = vfs_fsync_range(file, file->f_path.dentry,
+                               offset, end, 0);
+
+               if (err2 != -EINVAL)
+                       err = nfserrno(err2);
+               else
                        err = nfserr_notsupp;
-               }
        }
 
        nfsd_close(file);
+out:
        return err;
 }
 #endif /* CONFIG_NFSD_V3 */